Bleaching composition



Patented Jan. 4, 1938 UNITED STATES PATENT OFFICE BLEQCHIN G COMPOSITION tion of Delaware No Drawing. Application January 9, 1936. Serial No. 58,437

3 Claims.

This application relates to a novel composition for use in bleaching. More particularly, it

is concerned with an active oxygen yielding composition which is especially useful in the bleaching of textile materials and other substances requiring an alkaline bleach bath.

The active oxygen yielding compound, sodium peroxide, has been widely used as a bleaching agent for the bleaching of textile materials generally. However, while this is thecheapest commercial source of active oxygen, ordinarily solutions of sodium peroxide are too high in'alkalinity to be utilized for bleaching directly without neutralization. Accordingly, bleachers preparing solutions of sodium peroxide in water have found it first necessary to add an acid such as sulfuric acid to the solution in order that a dilute solution of hydrogen peroxide may result. The necessity of adding acid has required the bleacher to keep on hand an additional chemical agent and has been objectionable for that reason.

Moreover, when the bleacher utilizes an acid such as sulfuric acid for neutralizing the sodium peroxide solution, sodium sulfate is formed in the solution as one of the products. -When baths are used for the bleaching of cotton goods which I are subsequently dyed, the presence of sodium sulfate has been found objectionable in that it interferes with the satisfactory taking of the dye by the bleached goods in the subsequent dyeing operation.

Accordingly, we have succeeded in preparing an active oxygen yielding composition comprising sodium peroxide together with another ingredient which, when the mixture is dissolved in water, will result in a bleaching solution requiring no or practically no pH adjustment. The mixture of our invention is a solid powder which may be stored for long periods of time without any danger of deterioration or undue loss in active oxyen content.

One of the objects of this invention is to prepare a composition which will utilize the very desirable active oxygen-yielding compound, sodium peroxide, and which when dissolved in water will automatically. result in a bleach bath having the desired pH. Obviously then, in the bleaching of textile materials such as'cotton, baths prepared with the novel composition of this application will require no pH adjustment. While the addition of a material such as sodium silicate to the resulting bleach bath is not dispensed with by the use of our novel bleaching composition, the quantity ofthis material necessary may be less than is now customary since it is not added for the purpose of adjusting the pH but only in amount suflicient to supply the necessary silicate content to the bleaching solution.

Another of the objects of this invention is to 5 prepare a mixture which will be solid and which will readily and rapidly dissolve in water without excessive development of heat or loss in active oxygen to yield a solution of any specified and desired pH value. Still another object of 0 this invention is to prepare an active oxygenyielding composition involving a mixture of two or more ingredients which will be stable upon storage and which will not deteriorate nor lose active oxygen to a deleterious extent no matter 15 how long it is stored prior to utilization. Finally, yet another object of this inventionis to prepare a solid active oxygen-yielding composition which may be safely subjected to any temperature that may be normally encountered during the storage period without any danger of premature reaction, deterioration, or undue loss in active oxygen content.

While previously the preparation of a solid product which when dissolved in water will yield 25 a bleach bath of the required active oxygen content and which will still have the proper degree of alkalinity may have been vaguely contemplated from time to time, the solution of the problem of preparing this solid product has been 30 prevented by the difilculty of selecting a suitable acidic material which would function to reduce the high alkalinity resulting from the sodium peroxide when the latter is dissolved in water. In practice, when utilizing sodium peroxide, the 35 high alkalinity of the resulting solution is frequently reduced by the addition of sulfuric acid but this yields a sulfate in the solution and generally sulfates are undesirable because they interfere with proper dyeing of the bleached cot- 40 ton fabrics in subsequent operations. Moreover, sulfuric acid is not a solid and while solid acidic sulfates might conceivably be used they would also possess the undesirable effect of adding materials to the bath which interfere with subse- 45 quent dyeing. These factors led us to dismiss from consideration solid products containing sulfuric acid and solid sulfates.

Organic acids such as citric acid, which is a solid, have been suggested but generally organic acids are unsatisfactory because they are oxidized by the sodium peroxide upon standing and this may result in a product which is relatively unstable and may be subject to violent decomposition and possible explosion. The preparation of a solid mixture of sodium peroxide and a solid acid has been impeded by inability to find an acid or an acidic substance which would be entirely suitable and satisfactory under all conditions.

We have tried the solid acid, boric acid, the acid of commerce being orthoboric acid, HaBOa, and have found that it is possible to utilize mixtures comprising sodium peroxide and orthoboric acid. However, the boric acid of commerce, H3130: is not as compatible with sodium peroxide as might be desired. For example, if the mixture should reach a temperature within the range 60 to C. during storage, water is evolved from the orthoboric acid and obviously the presence of water in a mixture including sodium peroxide is entirely objectionable. Under some conditions we have found that mixtures which have been heated to a temperature within the range 60 to 80 C. on storage suffer appreciable and objectionable losses in active oxygen content and may, moreover, react to dissipate substantially all their active oxygen content. However, we do not mean to exclude the ordinary boric acid of commerce, orthoboric acid, entirely from-the purview of our invention as mixtures of sodium peroxide and this acid will be found quite satisfactory unless there is danger during the storage period that a temperature of above about 60 C. may be reached.

However, in the search for a suitable solid acid to mix with sodium peroxide so as to prepare a solid mixture which when dissolved in water will result in a solution possessing the pH value found desirable for bleaching operations, we have found that metaboric acid, H1302, is practically the ideal material. This acid is conveniently prepared from orthoboric acid, H3303, by heating it to a temperature of about the boiling point of water, C. At this temperature water is driven off and substantially anhydrous metaboric acid, HBOz, results.

Metaboric acid is entirely compatible with sodium peroxide in all proportions. When mixtures of the two are stored, difliculties due to undue active oxygen losses by decomposition do not arise. Moreover heating to an elevated temperature, such as 60 to 80 C., or to any other temperature which might reasonably be reached dur-..

ing the period of storage results in no deleterious effects. A mixture of metaboric acid and sodium peroxide when dispersed in water goes rapidly into solution without undue development of heat and without deleterious losses in active oxygen.

As previously stated in the bleaching of fabrics such as cotton with hydrogen peroxide solutions it has been found most suitable to maintain the pH of the solution at somewhere in the range 9.0 to 11.0 preferably around 10.0. For bleaching with the solid boric acid-sodium peroxide mixture of our invention we have found that a pH value of 10.0 is to be preferred but that the pH value may go slightly above this value or as high as 10.5 or 11.0 without affecting the quality of the result. Thus our invention is primarily concerned with the preparation of a mixture of metaboric acid and sodium peroxide which when dissolved in water will have a pH value of around 10.0 or slightly above. However, it is, of course, within the scope of our invention to prepare mixtures of the two ingredients, either alone or together with other materials, which when dissolved in water will result in solutions having any desired pH value whatever. Thus for the bleaching of some materials it may be advisable to maintain a somewhat higher pH, for example a pH value of 13.0 or 15.0 and our invention is to be construed to include a composition having any relative proportions of the two ingredients required to produce a solution, when the compound is dissolved in water, having any desired pH value whatever. Thus for some bleaching it may be desirable to add so much of the metaboric acid or orthoboric acid to the mixture that a solution having a pH value on the acid side will result, and this is, of course, within the purview of our invention.

When sodium peroxide and metaboric acid are dissolved in water the following reaction occurs:

NaBOz is produced and this salt yields a solution having a pH of approximately 10.0, or the alkalinity desired for the bleaching of textile materials such as cotton. From this equation it might be expected that a mixture having the relative proportions one mole of sodium peroxide and two moles of metaboric acid would result in a solution having the required pH value for bleaching of 10.0. This would require approximately 1.12 parts of metaboric acid to 1 part of sodium peroxide by weight. Surprisingly enough, in order that a pH value of about 10.0 be attained when the mixture is dissolved in water slightly over the theoretical quantity of metaboric acid is desirable and we prefer to utilize for cotton bleaching a mixture comprising 1.25 parts of metaboric acid to 1 part of sodium peroxide. However, we have utilized mixtures containing as high as 2.2 parts of metaboric acid to 1 part of sodium peroxide for cotton bleaching and the pH value of the solution resulting when such a .mixture is dissolved in water is not too high for eflicient economical and satisfactory bleaching.

Thus our invention involves, broadly, the utilization for bleaching purposes of a solid composition comprising sodium peroxide and boric acid in admixture. of the two boric acids, orthoboric acid and metaboric acid, while both may be used, we much prefer to utilize metaboric acid, I-lZBOz because of the considerations previously described.

The two ingredients of our novel composition may be employed in any relative proportions found desirable or necessary to result in solutions of any desired pH value when the composition is dissolved in water. For the bleaching of textile fabrics such as cotton, or other materials requiring a solution having a pH value of approximately 10.0, we have found that a mixture of 1.25 parts of metaboric acid to 1 part of sodium peroxide (by weight) is most suitable. However, mixtures containing as little as 1.1 parts of metaboric acid to 1 part of sodium peroxide have been used for cotton bleaching with success, and we have also employed mixtures comprising as high as 2.2 parts of metaboric acid to 1 part of sodium peroxide. Of course the novel compositions of this application are not to be construed as consisting solely or sodium peroxide and boric acid as various other ingredients, inert or otherwise, may also be present without interfering with the operation of our novel bleach baths.

It is to be understood that the proportions and amounts specified throughout this application are to be considered as illustrative and not restrictive, since various changes may be made in the composition of our novel product without departing from the scope or spirit of our invention.

The invention is not to be narrowly construed to require any'specific ratios but is to be construed solely in accordance with the appended claims.

We claim:

1. A solid composition for use in bleaching comprising sodium peroxide and metaboric acid.

2. A solid composition for use in bleaching comprising sodium peroxide and metaboric acid, there being present an amount of said metaboric acid ranging from 1.1 to 2.2 parts by weight for every part of sodium peroxide.

3. A solid composition for use in bleaching comprising sodium peroxide and metaboric acid, said metaboric acid being present in approximately 1.25 parts by weight for every part of sodium peroxide.

HARVEY N. GILBERT. IGNATIUS J. WERNERT. 

